docs: def structural_similarity(document_1, document_2):
      """
      Computes the structural similarity between two DOM Trees
      :param document_1: html string
      :param document_2: html string
      :return: int
      """
      try:
          document_1 = lxml.html.parse(StringIO(document_1))
          document_2 = lxml.html.parse(StringIO(document_2))
      except Exception as e:
          print(e)
          return 0
  
      tags1 = get_tags(document_1)
      tags2 = get_tags(document_2)
      diff = difflib.SequenceMatcher()
      diff.set_seq1(tags1)
      diff.set_seq2(tags2)
  
      return diff.ratio()